This invention relates generally to agricultural tractors towing implements, and, more particularly, to a connection mechanism for a tractor drawbar that provides roll and pitch freedom of movement between the tractor and the towed implement.
Pull type implements have been used in farming operations for decades. For example, the agricultural implement may be a mower designed to cut and process hay or other crops. The implement may also be configured as a forage harvester, hay recovery implement, baler, sprayer, or ground breaking implement. Typically, the implement is towed and powered by a towing vehicle such as a tractor. A powertake-off shaft (PTO) of the tractor typically provides mechanical power to the implement.
The implement is typically connected to the tractor by a pivoting draft tongue. There are two common methods of attaching the draft tongue of the implement to the towing vehicle. The first is to connect the draft tongue directly to the drawbar of the towing vehicle. A simple hitch pin can be used to drop through a hole in the draft tongue and into a hole in the towing vehicle drawbar. The implement tongue may also have a ball joint to allow freedom of rotation about the vertical (yaw) axis, the horizontal transverse (pitch) axis and the horizontal longitudinal (roll) axis or the hitch pin joint may be loose enough to allow the rotation needed. A shaft spans the hitch, extending from the tractor power take-off to the implement and must be sufficiently flexible to accommodate relative movement of the tractor and implement.
The second method is to use a swivel hitch on the implement. A swivel hitch incorporates the power take-off connection into the hitch connection, typically using a set of gearboxes, one above the other, with a connecting drive shaft between them. The gearboxes can swivel relative to each other. The relative swiveling motion becomes the vertical (yaw) axis of rotation. Typically, the swivel hitch has a frame member that pivots on the same yaw axis as the swivel gearboxes and connects to the three point hitch assembly or drawbar on the towing vehicle. The upper gearbox is fixed to the draft tongue. The lower gearbox and swivel hitch frame pivot relative to the upper gearbox and follow the tractor as it turns. Additional pivot members incorporated into the swivel hitch assembly allow relative pitch and roll freedom of movement between the tractor and the towed implement. One such mechanism is described in U.S. Pat. No. 6,776,432 issued on Aug. 14, 2004 to Harkcom, et al., the description portions of which are incorporated by reference herein.
Swivel hitches provide advantages over the standard pinned connection since the yaw axis is further behind the towing vehicle, allowing for much sharper turns than is permitted with a simple pinned drawbar connection. Swivel hitches are at a disadvantage since provisions for pitch and roll freedom must be incorporated into the hitch for each connected implement and present methods incorporating separate pinned joints for roll and pitch are not optimally economical.
It would be advantageous to provide an improved hitch adapter for use on a swivel hitch for an agricultural vehicle that provides for pitch and roll freedom of movement. Further advantages would be realized by a hitch adapter positioned on a tractor so that a single mechanism would provide freedom of movement for multiple implements connected by swivel hitch. Still further advantages would be realized by a hitch adapter that provides pitch and roll freedom of movement using a single pinned connection.